Sunroof on 89 300E

My sunroof has started to act up on my trusty 300E. It will "pop-up", but has to be pounded to get one corner back down. Also, it will not
slide back. You can hear it try, but it won't budge. The problem started when my wife pressed the button to slide it open when it was "popped" open.
Anybody got any idea's?
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